The only people calling it "breakthrough' are NWBO fanboys. No independent expert in the field would would call a highly manipulated clinical trial "breakthrough."
As NWBO has repeatedly stated, the naive OS data is confounded, the rGBM treatment arm was a post hoc data dredged outcome, not part of the original NAIVE GBM trial design. Then there was the mysterious FDA trial stop that the company has refused to identified the cause. No independent clinician would call all these issues and manipulations a credible trial. Only ones touting it have conflicts of interest and are receiving money directly or indirectly from NWBO. Sorry, not credible.
Your Viagra example also included a comprehensive clinical trial process including well-controlled, large-scale trials, not manipulated trials with confounded data, tossed out primary endpoint when it failed, etc. etc.